Application of calcium phosphate compounds, particularly hydroxyapatite as an artificial dental root, a bone prosthesis or a percutaneous device has been widely studied because of their excellent biocompatibility and capability of osteo-conductivity, and several kinds of these products have already been put into practical use. Bone prostheses include granules and pre-molded blocks. In particular, granular bone prostheses have been widely employed since they can be used to fill in a deficient part of any shape.
However, granular bone prostheses lack bonding properties among the granules thereof and are easily scattered and lost before they adhere to new bone. In order to overcome this disadvantage, a fibrin paste has been used to bond the granules to each other as described in JP-A-60-256460 and JP-A-60-256461 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). A fibrin paste, however, entertains a fear of infection with hepatitis virus, AIDS virus, etc. because it is prepared from human blood.
The present inventors have previously proposed a process for bonding granules containing .alpha.-tricalcium phosphate or tetracalcium phosphate as an essential component with an acid aqueous solution as disclosed in JP-A-2-1285 and EP-A-0324425. However, this technique is applicable only to those granules comprising .alpha.-tricalcium phosphate or tetracalcium phosphate.
The present inventors further proposed to use an aqueous solution of at least one of pullulan, glycol chitin, carboxymethyl chitin, and pectin, each of which does no harm to a living body, as a paste for bonding granules. This paste is suitable for in situ fixing of a granular bone prosthesis at the time of filling in a deficient part. However, such a paste is difficult to use to form pre-molded blocks from the granules because much time is required to evaporate the water content of the paste.